Republican presidential hopeful Donald Trump campaigned for a second straight day with a potential running mate, test-driving Indiana Governor Mike Pence on Tuesday before the expected announcement of his pick later this week.

It could be one of the most important decisions Trump makes on the campaign trail as he seeks to present a competent, steady wingman or woman to US voters after a turbulent primary season during which his provocative rhetoric frustrated many conservatives.

He will also be under pressure to name someone with political savvy and policy chops for the battle against the more experienced Hillary Clinton in the November election.

Stock in Pence, 57, has soared recently as someone who could provide the provocative billionaire with the steady tone that would neutralize Trump’s combativeness.

His deep resume would also counter the candidate’s political inexperience.

A handful of others are in the mix, including New Jersey Governor Chris Christie, a hard-nosed leader of a populous state, who campaigned with Trump in Virginia on Monday.

Former House speaker Newt Gingrich, who himself ran for president in 2012, is also on the short list.

“Newt is Newt. He’s a good guy,” Trump told the New York Times. Christie is “strong” while Pence is “solid as a rock.”

All eyes were on Pence as he took the stage ahead of Trump at an indoor sports complex where about 2,000 people stood on artificial turf.

Trump “gets it,” Pence told them. “Donald Trump hears the voice of the American people” and understands their “frustrations.”

“We’re tired of being told this is as good as it gets,” he added.

Trump appeared to appreciate the praise, teasing the crowd about what may lie in store for the governor.

“I don’t know whether he’s going to be your governor or your vice president. Who the hell knows?” he said to raucous cheers.

– Announcement this week –

Trump told the Times he was considering five choices, plus “two that are unknown to anybody.”

He said he aimed to announce his pick in the next three or four days, ahead of the Republican National Convention, which begins Monday in Cleveland and where Trump formally becomes the nominee.

As speculation ran rampant in the Republican “veepstakes,” one candidate with major buzz, Senator Bob Corker, removed himself from contention.

Gingrich compared running mate selection to “The Apprentice,” the hit reality show that Trump hosted for years on US television.

“You find out sooner or later who the last one standing is,” Gingrich said.

Pence is an unflappable Midwesterner, conservative, religious and measured.

He is a potential bridge to Congress, having served in the House of Representatives for a dozen years, entering the same year as current House Speaker Paul Ryan.

Pence is running for re-election, but under Indiana rules must decide by Friday whether to continue his campaign.

Pence’s team was dropping no hints.

“The governor has said on many occasions that it’s an honor to have his name in this discussion, but really his focus remains on serving Hoosiers as the governor of Indiana,” his deputy campaign manager Marc Lotter told AFP.

Some attending the Indiana event dismissed the VP talk altogether.

“I don’t care who Donald puts on there, because Donald is the one that deserves the vote,” argued Chris Rebuck, 44, who works in the mortgage industry.

And yet Rebuck acknowledged he wants Trump to name a running mate who can attract voters skeptical about a Trump candidacy.